The residential development in Area C shall include housing affordable to low and moderate income households. Twenty percent of the units must be reserved for, and affordable to, low or moderate income households. Of these, at least half must be reserved for, and affordable to, low income households. The developer may designate that the low and moderate income units will be rental units. If the developer designates that the low and moderate income units are rental units, at least 26 percent of the low income units must be reserved for, and affordable to, very low income households. Low and moderate income units designated as rental units shall be maintained as rental units for a period of at least 30 years.